Seismic activity at Kasatochi volcano continues to slowly decline following the eruptions on August 7. Possible intermittent tremor occurred for several hours on August 27 and was detected by the AVO seismic network on Great Sitkin Island 25 miles west of Kasatochi. Satellite views were cloudy this week.

The volcano remains in a restless condition and is hazardous to approach. Further explosive activity remains possible.

Seismicity at Okmok volcano has declined and significant ash plumes have not been observed since August 19. The Aviation Color Code/Alert Level was reduced to YELLOW/Advisory on August 27. A clear satellite view on August 28 showed a weak steam plume and a weak thermal anomaly. Although the level of seismicity has declined and it appears that ash is no longer being erupted, it is possible for vigorous ash emissions to resume at any time.

Visual observations of the caldera floor made on August 23 indicate that low level eruptive activity has also likely stopped. It is possible for vigorous ash emissions to resume at any time.

Satellite views were most cloudy this week. A weak thermal anomaly was detected on August 24. The lack of recent activity prompted AVO to lower the Aviation Color Code/Alert Level to YELLOW on August 25.

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

VOLCANO ALERT LEVELS

NORMALVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

ADVISORYVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCHVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.

WARNINGHazardous eruption is imminent, underway, or suspected.

AVIATION COLOR CODES

GREENVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

YELLOWVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

ORANGEVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].

REDEruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].